linux-kernel - Re: [PATCH v7 02/15] sched/core: uclamp: Enforce last task UCLAMP

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 13 Mar 2019 18:29:11 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Patrick Bellasi <patrick.bellasi@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-api@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Tejun Heo <tj@...nel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Paul Turner <pjt@...gle.com>,
        Quentin Perret <quentin.perret@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Todd Kjos <tkjos@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Steve Muckle <smuckle@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>
Subject: Re: [PATCH v7 02/15] sched/core: uclamp: Enforce last task UCLAMP_MAX

On Wed, Mar 13, 2019 at 04:20:51PM +0000, Patrick Bellasi wrote:
> On 13-Mar 15:10, Peter Zijlstra wrote:
> > On Fri, Feb 08, 2019 at 10:05:41AM +0000, Patrick Bellasi wrote:
> > > +uclamp_idle_value(struct rq *rq, unsigned int clamp_id, unsigned int clamp_value)
> > > +{
> > > +	/*
> > > +	 * Avoid blocked utilization pushing up the frequency when we go
> > > +	 * idle (which drops the max-clamp) by retaining the last known
> > > +	 * max-clamp.
> > > +	 */
> > > +	if (clamp_id == UCLAMP_MAX) {
> > > +		rq->uclamp_flags |= UCLAMP_FLAG_IDLE;
> > > +		return clamp_value;
> > > +	}
> > > +
> > > +	return uclamp_none(UCLAMP_MIN);
> > 
> > That's a very complicated way or writing: return 0, right?
> 
> In my mind it's just a simple way to hardcode values in just one place.
> 
> In the current implementation uclamp_none(UCLAMP_MIN) is 0 and the
> compiler is not in trubles to inline a 0 there.
> 
> Is it really so disgusting ?

Not disguisting per se, just complicated. It had me go back and check
wth uclamp_none() did again.